I would highly recommend doing research on blogs, these forums, and elsewhere for the questions you are likely to get in your interview! Then open a Word document and start typing out some answers, even if just in bullet point form. You can have this open in front of you as your "cheat sheet" during the interview to keep from drawing blanks, it really helped me!
You WILL get the question about why you want to do the CP and some variant of how your past work experience qualifies you for it. Knock those questions out of the park (without sounding too scripted) and you're off to a great start. Play Disney music while waiting for the call, to help calm your nerves! It's okay to sound a tiny bit nervous, but focus on being cheerful and enthusiastic and they will pick up on that!
Also, I should mention the web-based interview, which comes first and does weed out a few people. It's very easy if you keep in mind two things: 1. Keep your answers consistent (they'll ask you the same question in a slightly different way) and 2. Answer "strongly agree" and "strongly disagree" as much as possible! Even if you don't feel incredibly strongly about a statement, Disney is looking for people who know themselves. Those two tips helped me breeze through the WBI!
Good luck!